1. Field of the Invention
The present invention relates to the selective chlorination of meta-dihalobenzenes, and, more especially, to such chlorination by reacting a meta-dihalobenzene with a chlorine donor, in the presence of at least one alkali metal amide and at least one compound adapted to complex the cation of said alkali metal amide.
2. Description of the Prior Art
Various processes for the chlorination of halogenated compounds employing an acid catalyst are of course well known to this art.
Thus, the chlorination of such halo-compounds by means of gaseous chlorine in the presence of ferric chloride or aluminum chloride is representative. Compare, in particular, C. A. Thomas, Anhydrous Aluminum Chloride in Organic Chemistry (Reinhold Publishing Corporation).
The presence of a halogen atom on the aromatic nucleus orients, under the aforenoted conditions, the chlorination to ortho, para-. Experimentally, preferential chlorination in the para-position is observed.
As regards the meta-dihalocompounds, the chlorination thereof is essentially of the 4-position. For example, chlorination of meta-dichlorobenzene principally yields 1,2,4-trichlorobenzene.
Selective chlorination of the 2-position cannot be carried out in this manner. Such compounds have been obtained in the prior art only by indirect means.